The present invention relates generally to devices and methods for delivering therapeutic or diagnostic agents to a portion of the human body. More particularly, the present invention relates generally to devices and methods for delivering and injecting fluid into heart tissue.
Injection catheters may be used to inject therapeutic or diagnostic agents into a variety of organs, such as the heart. In the case of injecting a therapeutic agent into the heart, 27 or 28 gauge needles are generally used to inject solutions carrying genes, proteins, or drugs directly into the myocardium. A typical volume of an agent delivered to an injection site is about 100 microliters. A limitation to this method of delivering therapeutic agents to the heart is that the injected fluid tends to leak from the site of the injection after the needle is disengaged from the heart. In fact, fluid may continue to leak over several seconds. In the case of dynamic organs such as the heart, there may be more pronounced leakage with each muscle contraction.
Many medical procedures involve the delivery of therapeutic and diagnostic agents to a targeted portion of a patient""s body. For example, the delivery of a therapeutic agent is used in the treatment of esophageal varices, a condition where blood vessels of the esophagus are enlarged and may potentially burst. For such a procedure, a therapeutic agent is injected into the varix. When treating an esophageal varix, the agent may be a coagulant such as sodium morrhuate. When a coagulant is injected into a varix, it causes it to occlude. An injection catheter may be used to deliver the therapeutic agent in order to minimize the invasive nature of the procedure.
In a similar procedure, an injection catheter may be utilized in the treatment of ulcers in the stomach lining. With such treatment, an injection catheter may be used to deliver drugs such as sclerosing or vasoconstrictive agents. These drugs typically clot or occlude the bleeding tissue to stop bleeding or to reduce the possibility of a blood vessel bursting.
As mentioned previously, injection catheters may also be used to inject therapeutic or diagnostic agents into the heart. A limitation to this method of delivering therapeutic agents to the heart is that the injected fluid tends to leak from the site of the injection after the needle is disengaged from the heart. In fact, fluid may continue to leak over several seconds. In the case of the heart, there may be more pronounced leakage with each muscle contraction.
Therapeutic and diagnostic agents may be delivered to a portion of the heart as part of a percutaneous myocardial revascularization (PMR) procedure. PMR is a procedure which is aimed at assuring that the heart is properly oxygenated. Assuring that the heart muscle is adequately supplied with oxygen is critical to sustaining the life of a patient. To receive an adequate supply of oxygen, the heart muscle must be well perfused with blood. In a healthy heart, blood perfusion is accomplished with a system of blood vessels and capillaries. However, it is common for the blood vessels to become occluded (blocked) or stenotic (narrowed). A stenosis may be formed by an atheroma which is typically a harder, calcified substance which forms on the walls of a blood vessel.
Historically, individual stenotic lesions have been treated with a number of medical procedures including coronary bypass surgery, angioplasty, and atherectomy. Coronary bypass surgery typically involves utilizing vascular tissue from another part of the patient""s body to construct a shunt around the obstructed vessel. Angioplasty techniques such as percutaneous transluminal angioplasty (PTA) and percutaneous transluminal coronary angioplasty (PTCA) are relatively non-invasive methods of treating a stenotic lesion. These angioplasty techniques typically involve the use of a guidewire and a balloon catheter. In these procedures, a balloon catheter is advanced over a guidewire such that the balloon is positioned proximate a restriction in a diseased vessel. The balloon is then inflated and the restriction in the vessel is opened. A third technique which may be used to treat a stenotic lesion is atherectomy. During an atherectomy procedure, the stenotic lesion is mechanically cut or abraded away from the blood vessel wall.
Coronary by-pass, angioplasty, and atherectomy procedures have all been found effective in treating individual stenotic lesions in relatively large blood vessels. However, the heart muscle is perfused with blood through a network of small vessels and capillaries. In some cases, a large number of stenotic lesions may occur in a large number of locations throughout this network of small blood vessels and capillaries. The tortuous path and small diameter of these blood vessels limit access to the stenotic lesions. The sheer number and small size of these stenotic lesions make techniques such as cardiovascular by-pass surgery, angioplasty, and atherectomy impractical
When techniques which treat individual lesion are not practical percutaneous myocardial revascularization (PMR) may be used to improve the oxygenation of the myocardial tissue. A PMR procedure generally involves the creation of holes, craters or channels directly into the myocardium of the heart. In a typical PMR procedure, these holes are created using radio frequency energy delivered by a catheter having one or more electrodes near its distal end. After the wound has been created, therapeutic agents are sometimes injected into the heart chamber from the distal end of a catheter.
Positive clinical results have been demonstrated in human patients receiving PMR treatments. These results are believed to be caused in part by blood flowing within a heart chamber through channels in myocardial tissue formed by PMR. Increased blood flow to the myocardium is also believed to be caused in part by the healing response to wound formation. Specifically, the formation of new blood vessels is believed to occur in response to the newly created wound. This response is sometimes referred to as angio-genesis. After the wound has been created, therapeutic agents which are intended to promote angio-genesis are sometimes injected into the heart chamber. A limitation of this procedure is that the therapeutic agent may be quickly carried away by the flow of blood through the heart.
In addition to promoting increased blood flow, it is also believed that PMR improves a patient""s condition through denervation. Denervation is the elimination of nerves. The creation of wounds during a PMR procedure results in the elimination of nerve endings which were previously sending pain signals to the brain as a result of hibernating tissue.
The present invention relates generally to devices and methods for delivering therapeutic or diagnostic agents to a portion of the human body. More particularly, the present invention relates generally to devices and methods for delivering and injecting fluid into heart tissue.
A catheter in accordance with the present invention includes a first elongate shaft having a distal end, a proximal end, and a lumen therethrough. The first elongate shaft includes a first curved portion proximate the distal end of the first elongate shaft. In a preferred embodiment, the radius of the first curved portion of the first elongate shaft is selected so that the distal end of the first elongate shaft will be disposed within a wall of an organ (e.g., the heart) during an injection procedure in accordance with a method of the present invention. The first curved portion of the first elongate shaft defines a first plane.
In one embodiment of the invention, the first elongate shaft also includes a second curved portion disposed between the distal end of the first elongate shaft and the first curved portion of the first elongate shaft. The second curved portion of the first elongate shaft defines a second plane which intersects the first plane at an angle. In a preferred embodiment, the second plane is substantially orthogonal to the first plane. This arrangement reduces the likelihood that the distal end of the first elongate shaft will perforate the wall of an organ (e.g., the heart) during an injection procedure in accordance with a method of the present invention.
In one embodiment of the present invention, a second elongate shaft is slidingly disposed within the lumen of the first elongate shaft. In this embodiment, the second elongate shaft may include a curve defining a third plane. In a preferred embodiment, the third plane is substantially orthogonal to the first plane. This arrangement reduces the likelihood that the distal end of the second elongate shaft will perforate the wall of an organ (e.g., the heart) during an injection procedure in accordance with a method of the present invention.
During an injection procedure in accordance with a method of the present invention both the first elongate shaft and the second elongate shaft may be advanced into a target tissue. After the injection of fluid into the target tissue, the first elongate shaft and the second elongate shaft may be withdrawn from the target tissue. In a preferred embodiment, the first elongate shaft and the second elongate shaft each include a plurality of curves. The tortuous path defined by the first elongate shaft and the second elongate shaft reduce the likelihood that injected fluid will escape from the target tissue after the first elongate shaft and the second elongate shaft are disengaged from the target tissue.